Ponds attract wildlife to the garden and can provide an oasis of life for aquatic organisms, but not all visitors are as welcome as others…

WORDS: JEREMY GAY

We all love wildlife and, unlike an aquarium, a pond can attract visitors that are free to travel to and from the water at will. But which are desirable and which are a downright nuisance?

It all comes down to whether you want a fish pond or a wildlife pond — the two are very different things, and what benefits one may not benefit the other.

If you have fish in your pond they must be your number one welfare priority. Unlike insects, amphibians and birds, they can’t leave and that makes them sitting ducks for all manner of predators. What makes it worse is that we then handicap them with bright colours, fat bodies and a lack of hiding places or distance to escape to.

Here’s the list of regular offenders:

Herons can wipe out all the fish in your pond in no time. Image by Shutterstock.

Heron

Public enemy number one has got to be the heron. These lanky grey birds will frequent your pond before you get up in the morning, and with no one about, having your pond close to your house is no defence either. Once they’ve found your pond they can more or less empty it of small to medium sized fish, and stab and injure those too large to swallow.

Prevention

You can’t harm them as they are protected (although you should never think of doing that anyway).

Netting can be effective but it would have to be fine, taut and effectively cover all areas.

Fishing line placed strategically around the pond on stakes can prevent a bird from landing or wading in. Wire can also be placed at pergola height to prevent flying down to the pond.

Plastic herons are the most commonly practiced defence, although we have heard many stories of owners seeing a live heron feeding next to their plastic one!

Cure

Very visible fish in the pond will be targeted first and are easy to spot from the air. Try mottled Shubunkins instead of bright red goldfish, but failing that, netting is the only way.

Cute they may be, but otters are being increasingly reported as filling their bellies on goldfish and Koi. Image by Shutterstock.

Otter

I believe that otters have as much right to the waterways as we do, but I can imagine how gutting it would be to find your prize Koi massacred of a morning. Otters are well and truly back, and gorging themselves on ornamental fish all over the UK.

Prevention

Netting a pond won’t work, as otters will crawl under it. Instead, you’ll need a wooden frame with no gaps, and a wooden frame with wire mesh on top, with a latch or even a padlock on it.

Cure

Build a waist-high wall or fence around the whole pond, or opt for a raised, formal pond with the frame and mesh top.

Rats

Rats are great swimmers, and ponds provide lots of feeding opportunities for them, including eating your fish food. They are a menace though, chewing through pond liners and weeing in the water, spreading Weil’s disease to humans, which at best is flu like but can be much worse. They can predate on other animals, too — I’ve seen them taking baby ducks, so they may have a go at a sluggish fish.

Prevention

Don’t leave buckets of pond food poolside, and don’t leave uneaten food on or around the pond. Having bird feeders near the pond may attract them, too.

Cure

Brick-built raised ponds with no exposed liner and no subterranean access to the liner either, solved by a concrete base.

Small gauge wire mesh.

Many pondkeepers would probably be willing to sacrifice the odd small fish for a glimpse of a kingfisher in their garden. Image by Alamy.

Kingfisher

One of my all time favourite birds, a kingfisher is a wonderful sight. Even the most staunch pondfish breeder surely can’t deny such a handsome and diminutive bird the odd snack, so I say them let them stay and enjoy the moment. They’ll only predate on small, minnow sized fish anyway.

Prevention

You are unlikely to have kingfishers if your pond is nowhere near a river or stream — so you could move!

Cure

If you want to say ‘bah humbug’ to ever having a kingfisher visit, or your fry happen to be tategoi or tosakin worth a few hundred quid a pop, simply cover the water with fine netting or a plastic corrugated lid.

Damsel and dragonflies are stunning to see flitting around your pond, but their larvae will predate on baby fish. Image by Shutterstock.

Damsel and dragonflies

Only dangerous to your fish when they are fry, damsel and dragonfly larvae are voracious predators which may take tadpoles and baby fish.

Prevention

Don’t have any plants and heavily filter the pond. A clinically clean Koi pond with large hungry Koi is unlikely to support any dragonfly larvae, as the fish will eat them.

Cure

Remove all plants and if you are particularly wanting to raise Koi and goldfish fry, very small gauge insect netting will keep the adult insects from laying their eggs in the water. But really, the visual benefit of adults often outweighs the few fry you could lose to their larvae.

Cormorants will soon polish off those Koi if given the chance. Image by Shutterstock.

Cormorants

These 'sea' birds travel inland the world over in search of food, and can gobble up fish on an industrial scale. If a cormorant lays eyes on your pond and can access it, your fish are in trouble.

Prevention

Stop the bird from flying in, perching and diving into the pond.

Cure

High level netting or wire to prevent flight in, and very coarse netting, securely fastened to prevent the birds taking fish. Make sure the net gauge is fine enough to prevent the beak, head or neck from poking through it and grabbing or stabbing fish.

Ducks are endearing but they can make a real mess of your pond. Image by Shutterstock.

Ducks

Wild ducks finding your ornamental pond is a wonderful thing for all of about five minutes. They get all excited, wade in and start to dabble and bathe. If you have a waterfall they may play in it — and even climb up and ride back down it! But by the time you’ve rushed to grab that camera, the idyllic scene will have turned into carnage as the ducks start to demolish all your pond plants, uproot the soil in the plant baskets and poo and drop soil into the water, making an instant mess. Your fish will scatter too.

Prevention

You need to prevent ducks from both flying in and entering the pond.

Cure

Net the pond high up to prevent ducks flying in, and also at water level to prevent them from wading in. And don’t be tempted to feed the ducks — they will come back.

Grass snakes may take a dip in your pond during hot weather and will occasionally take the odd small fish. Image by Shutterstock.

Grass snakes

During heat waves, grass snakes may take to the water to cool down. They can hold their breath and swim underwater, and are reported to occasionally predate pond fish.

Prevention

A grass snake won’t wipe out a pond like a heron or otter, and if you have the kind of undergrowth that encourages grass snakes, you’ll probably have frogs and toads too, which the snakes will eat instead. The defence is to prevent access for the snake.

Cure

Why would you want to stop grass snakes from thriving in your garden? Native reptiles are so cool and grass snakes are not in the least bit dangerous. But if you want to stop them, a waist high brick built raised pond will do it. They tend to prefer ground level water with poolside vegetation to retreat to.

Larger Koi and goldfish will be safe from crows. Image by Shutterstock.

Crows

In my retail days we regularly fought a very clever crow, which could tell the time and would wait until closing time, before it swept in. Its favourite prey were 5–7.5cm/2–3in Comet goldfish which it would pick from the water, always leaving the head for us in the morning as evidence (herons and cormorants always swallow fish whole, head first).

Prevention

You’ll be OK with foot-long fish. Understocking the pond will also not so be as tempting. Feed fish away from the pond edge, as the crow can’t reach very far.

Cure

Net your pond or use a frame and cover, which you can hinge up and down depending on whether you are in the garden or not.

Water scorpions will predate fry, but bigger fish will eat them. Image by Shutterstock.

Water scorpion

A pretty menacing, quite large aquatic insect, the water scorpion can and does consume large tadpoles, baby newts and pond fish fry.

Prevention

The water scorpion will favour sluggish, weedy areas where it can hide and ambush fish, and where smaller fish like to hang out.

Cure

Don’t introduce any plants, stock large fish only, which will eat them, and regularly vacuum your pond walls and base.

Mink are unlikely to turn down a free and easy fish supper. Image by Shutterstock.

Mink

I’ve never seen a wild otter, but I saw plenty of mink in the waterways when I was growing up. Mink are indiscriminate pond fish killers and should be treated in the same way as otters. If a mink finds your pond all your fish are in trouble — and chickens if you keep them, too.

Prevention

As with the otter, you need to totally block entry to your pond and even small gaps or holes in netting will allow easy entry.